[Rachel's Introduction: Here's a third important development: On December 18, a California company began "printing" solar photovoltaic cells onto thin aluminum foil, thus driving down the costs of solar-electric panels to be competitive with coal plants.]

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By John Vidal, environment editor The Guardian

The holy grail of renewable energy came a step closer yesterday [actually, December 18, 2007] as thousands of mass-produced wafer-thin solar cells printed on aluminium film rolled off a production line in California, heralding what British scientists called "a revolution" in generating electricity.

The solar panels produced by a Silicon Valley start-up company, Nanosolar, are radically different from the kind that European consumers are increasingly buying to generate power from their own roofs. Printed like a newspaper directly on to aluminium foil, they are flexible, light and, if you believe the company, expected to make it as cheap to produce electricity from sunlight as from coal.

Yesterday Nanosolar said its order books were full until mid-2009 and that a second factory would soon open in Germany where demand for solar power has rocketed. Britain was unlikely to benefit from the technology for some years because other countries paid better money for renewable electricity, it added.

"Our first solar panels will be used in a solar power station in Germany," said Erik Oldekop, Nanosolar's manager in Switzerland. "We aim to produce the panels for 99 cents a watt, which is comparable to the price of electricity generated from coal. We cannot disclose our exact figures yet as we are a private company but we can bring it down to that level. That is the vision we are aiming at."

He added that the first panels the company was producing were aimed for large-scale power plants rather than for homeowners, and that the cost benefits would be in the speed that the technology could be deployed. "We are aiming to make solar power stations up to 10MW in size. They can be up and running in six to nine months compared to 10 years or more for coal-powered stations and 15 years for nuclear plants. Solar can be deployed very quickly," said Oldekop.

Nanosolar is one of several companies in Japan, Europe, China and the US racing to develop different versions of "thin film" solar technology. It is owned by internet entrepreneur Martin Roscheisen who sold his company to Yahoo for $450m and, with the help of the founders of Google, the US government and other entrepreneurs in Silicon Valley, has invested nearly $300m in commercialising the technology.

At the moment solar electricity costs nearly three times as much as conventional electricity to generate, but Nanosolar's developments are thought to have halved the price of producing conventional solar cells at a stroke.

"This is the world's lowest-cost solar panel, which we believe will make us the first solar manufacturer capable of profitably selling solar panels at as little as 99 cents a watt," said Roscheisen yesterday.

However, the company, which claims to lead the "third wave" of solar electricity, is notoriously secretive and has not answered questions about its panels' efficiency or their durability. It is quite open about wanting to restrict access to the technology to give it a market advantage.

Jeremy Leggett, chief executive of Britain's leading solar energy company, Solar Century, said that it would be "breathtaking" if the technology proved as efficient as projected by the company. "This is a revolution. But people are going to be amazed at other developments taking place in solar technologies. We will be thrilled if this technology is as efficient as the company says. It will not change the direction of solar power in itself. Spectacular improvements are also being made in other parts of the industry," he said.

Figures released yesterday by the Earth Policy Institute in Washington showed that solar electricity generation was now the fastest-growing electricity source, doubling its output every two years. It is now attracting government and venture capital money on an unprecedented scale.

The technology is particularly exciting because it can be used nearly everywhere. "You are talking about printing rolls of the stuff, printing it on garages, anywhere you want it. It really is a big deal in terms of altering the way we think about solar," said Dan Kamman, director of the Renewable and Appropriate Energy Laboratory at the University of California at Berkeley.

"The next industrial revolution will be based on these clean green technologies," said Tony Juniper, director of Friends of the Earth. "If the UK wants to be part of it, as Gordon Brown says it does, then it needs to rethink its strategies. Ministers have so far shown a distinct lack of vision."

Sidebar: Power from light

Photovoltaic (PV) devices convert light into electrical energy. PV cells are made of semiconductor materials such as silicon. When light shines on a PV cell, the energy is transferred to electrons in the atoms of the PV cell. These electrons become part of the electrical flow, or current, in an electrical circuit. First wave photovoltaic cell used thick silicon-wafer cells but were cumbersome and costly. The second generation of photovoltaic materials were developed about 10 years ago and use very thin silicon layers. These brought the price down dramatically but still need expensive vacuum processes in their construction. The third wave of PV, now being developed by firms such as Nanosolar, can print directly on to other materials and does not use silicon.